The present invention concerns vehicle bumper constructions adapted to provide a consistent front (or rear) impact strength and energy absorption, even where the impact forces are angled relative to a longitudinal centerline of a vehicle. In particular, the present vehicle bumper construction is adapted to provide a more consistent energy absorption during catastrophic front impact, despite the angle or location of engagement by the colliding object.
Vehicle bumpers are designed to withstand considerable impact forces and further, where the impact is severe enough to cause damage, are constructed to absorb energy to reduce damage to the vehicle. An important part of the bumper construction includes the vehicle attachment towers that are used to support the bumpers on the vehicle frame. A problem is that the impact forces generated during a vehicle crash are not always centered on the bumper, and further are not always parallel a longitudinal centerline of the vehicle. When imbalanced and off-centered impact forces occur, there is a risk that the attachment towers that support the bumper on the vehicle frame may distort in a "parallelogram" like fashion instead of crushing like an accordion. A parallelogram-like collapse is undesirable, since it typically absorbs much less energy than an accordion-like collapse. The reason is because in a parallelogram-like collapse, the tower material bends only at opposing ends of the tower (i.e., only bends at a front end near the bumper and at a rear end adjacent the vehicle attachment). Contrastingly, in an accordion-like collapse, the tower material bends and crumples along multiple locations including locations between the ends, with each of the bending locations absorbing energy from the crash. It is undesirable to have a low energy absorption because an important purpose of the bumper system is to absorb energy before the vehicle itself begins to undergo damage. Often, depressions, notches, and other features are added to towers to help ensure that the towers will collapse in an accordion-like fashion as intended. However, even when these depressions, notches, and the like are included, they do no good if the tower collapses in a parallelogram-like manner. For example, this problem can occur when the impacting object strikes the bumper at an angle, such that the forces generated cause the bumper to shift laterally at the towers. This lateral shifting results in the bumper towers being placed under shearing/torsional forces causing the towers to fail by a parallelogram-like collapse. (For example, see FIG. 2.)
Another problem is that modern vehicles are often provided with aerodynamically shaped curvilinear bumpers that wrap around a front (or rear) of a vehicle, with the bumpers having end sections that wrap rearwardly at the vehicle fenders. The above-mentioned bumper towers are attached to the vehicle frame at locations spaced inboard of ends of the bumpers. During a center impact, these bumpers can elastically flex and straighten out somewhat before permanent deformation and/or before catastrophic failure occurs, pushing the vehicle attachment towers in an outboard direction. (For example, see FIG. 1.) This also results in the towers experiencing forces that cause the towers to parallelogram instead of crush with an accordion-like motion. This in turn results in a low energy absorption, which is undesirable.
In addition to the above, there are many government standards for testing bumpers and regulations governing the minimum strength required. Regulating governmental agencies (and also insurance companies) are continuing to improve the test standards and requirements, so that the tests more accurately represent the real world forces that result during a vehicle crash. Further, there are some tests now under consideration that will require improved bumper strength during angled and/or corner impact. The net result is that improved bumper constructions are needed to pass these bumper tests, both in terms of improved load bearing capabilities and also in terms of consistency of energy absorption. Bumper constructions are already very expensive, and it is undesirable in the highly competitive industry of automobile and vehicle manufacture to add even more cost and weight to bumper systems.
Therefore, an improved bumper construction is desired solving the aforementioned problems and providing the aforementioned advantages.